At present, with development of communications networks and rapid increase of service bandwidths in service bearer networks, a service switching system based on an electrical clustering technology emerges. The system includes multiple large-capacity service processing subracks that are interconnected and controlled using unified software. The system is manifested as a single device, that is, a network node.
Further, a physical architecture of the service switching system based on an electrical clustering technology is shown in FIG. 1, including multiple service processing subracks 101 (designated as service processing subrack 1, service processing subrack 2, . . . , service processing subrack m) and multiple electrical switching subracks 102 (designated as electrical switching subrack 1, electrical switching subrack 2, . . . , electrical switching subrack n). The service processing subracks 101 are connected to the electrical switching subracks 102 using optical fibers, and service interworking between the service processing subracks 101 is performed via the electrical switching subracks 102. Any inter-subrack service requires two service processing operations and one electrical switching operation.
An inter-subrack connection structure of the service switching system in FIG. 1 is shown in FIG. 2. An electrical signal output by a first service processing subrack 201 is converted into an optical signal using a first electrical-to-optical conversion module (E/O) 202, and the optical signal is transmitted to a first optical-to-electrical conversion module (O/E) 203 using an optical fiber. The first O/E 203 converts the optical signal into an electrical signal, and outputs the electrical signal to an electrical switching subrack 204. After performing electrical switching, the electrical switching subrack 204 outputs the electrical signal to a second E/O 205. The second E/O 205 converts the electrical signal into an optical signal, and transmits the optical signal to a second O/E 206 using an optical fiber. The second O/E 206 converts the optical signal into an electrical signal, and outputs the electrical signal to a second service processing subrack 207. In this way, service switching is completed.
Because service processing subracks are connected using an electrical switching subrack, one electrical switching subrack and four optical modules are required for each service switching, with the costs of two optical-to-electrical conversions, two electrical-to-optical conversions, and one electrical switching. Therefore, to ensure non-blocking switching, total interconnection bandwidth of the optical modules for inter-subrack connection needs to be twice total amount of system service access bandwidth, and total capacity of switching network chips in the electrical switching subrack also needs to be the same as the total system service access bandwidth.
It can be learnt that, such a clustering-based service switching system makes energy consumption, weight, and a volume of the system distributed, and reduces deployment difficulty. However, the large-scale electrical clustering technology-based inter-subrack connection brings relatively high extra costs and additional power consumption. Therefore, it becomes quite necessary to better reduce interconnection costs of the clustering-based service switching system.
In addition, in the electrical clustering technology-based service switching system, when service processing subracks need to provide a larger inter-subrack connection bandwidth, rates of the optical modules between the service processing subracks and the electrical switching subrack need to be increased. In this case, a larger-capacity service processing chip and a higher-rate interface module need to be selected for the service processing subracks. Moreover, the electrical switching subrack needs to be upgraded accordingly, to adapt to the change of the service processing subracks. That is, larger-capacity switching network chips and a higher-rate interface module also need to be selected for the electrical switching subrack. This brings a concurrent upgrade of the service processing subracks and the electrical switching subrack, and results in relatively high costs of system upgrading.